D2 V8 economy pain

[4X4V8]

I am dissapointed in the fuel economy of my D2 V8. I hardly use the thing so my contribution to global warming is less than the average hatchback driven the national average distance, so from that and a cost perspective it is irrelevant. I just want it running as efficiently as possible.

So I can't get over the fact that I am averaging 26.7L/100km in the city driving short distances. I may only be going to the next suburb, but am driving like a granny.

The reason I feel it's not right is that the previous D2 I had was exactly the same except an auto, not manual, and it would climb to 22-23L/100km, but that was in peak hour traffic, flooring it off the lights etc. I think I might've seen 24L/100km once.

I could get a best of 12.9L/100km on a trip to Canberra loaded up in the previous D2, it would easily average mid-13s on such a trip. This one I've hardly driven anywhere but on the M4 I got it down to 15L/100km - not too bad.

It has a slight miss just off idle if its under slight load (slow 2nd gear 90 degree corner, for example), the air filter looked dirty but I have just replaced it. Plugs are on order from the US and so I am hoping that's the silver bullet.

Anything else it could be? This is a low-kay car (now 89,000km) so maybe a good thrash with injector cleaner in it (and new plugs) might help? It seems to run okay except the hesitiation/miss.

I have driven many D1/D2s over the years and maybe I have to be prepared to accept that some are just thirstier than others. I seem to remember averaging 17L/100km on secondary dirt roads and freeway driving in one particular example I had, a D2a HSE.

[long stroke]

An average of 26.7lt does not sound right to me:eek:

[simonr23]

the car will use alot more fuel during short trips when the engine/gearbox(es) havent had a chance to warm up. if u try the same route a few times with the car at operating temps it should improve a noticable(although still v8 thirsty) amount. in your first post it sounds like this is a different route than the one you did in the old d2.

[4X4V8]

Assumption is the mother of all **ck-ups as they say, and I assumed cos this car was dealer serviced and low kays it should all be tip-top. Yeah, right.

Had some time to take a proper look in the dark under the bonnet tonight and the lead to cyl 1 is tracking like crazy and the connection to the spark plug is badly corroded. No wonder it's chewing fuel - and airfilter was filthy, too. Car has done 2000km since its last service (abt a year ago).

Any truth to the rumour that only OE leads suit the Champion OE plugs? I don't know where I got that from, but I'd like to look at Magnecor leads to replace the originals, which are the originals judging by the 98 date stamp on one lead, at least.

So new leads and new Platinum plugs for starters, and I am going to stay away from the Trive oops, the service centre that has serviced it all its life. Am going to try the mob in Homebush, they look like they might be okay. Just wish I had more time to service it myself. It ain't rocket science, but I'm a pedant and really slow. I'd do no work and go broke but have an excellently maintained Disco.

BTW, anyone know how long the platinum plugs are supposed to last? I have tried digging thru Rave and my owner's book and seemed to think it was 120,000km. Someone told me today it should be 80,000km.

[Pedro_The_Swift]

I worked it out to about 4 years inbetween plug replacement,,(80,000)
which is probably long enough to save up for the next set of platinums and magnacores:p



(FWIW I wouldnt put a champion plug in a lawnmower,,:angel:)

[4X4V8]

What's the best deal on Magnecors in Aus? I can get them from the US for abr $120 plus shipping abt $40 but if it's not much more may as well go local.

Pedro, you're talking Bosch Platinum? No-one likes the OE Champions?

[4X4V8]

Just got some fault codes come up on the ScanGauge. PO171 and PO174 - which according to a website I found in the US, it means both banks are running too lean.

Hmmm...

[tempestv8]

I've found that the Mass Air Flow sensor can degrade over time to the point where the engine is just running poorly, typically very rich. Same goes for the O2 sensors - the Bosch system will default to rich running if the sensors are out, yet no "check engine" light ever comes on.

So you can try replacing the O2 sensors as well as the MAF sensor.

The other area could be a stuck thermostat running, running the engine cool all the time? Only way to really tell is to put an OBDII scanner on and check the water temperature.

Buy a SCANGAUGE II and you'll be able to get accurate water temp readings. It should be fully warmed up around 92 to 98 degrees C.

Is your radiator fan viscous coupling siezed? You'll be able to hear a roaring fan and that will yield poor fuel consumption due to unnecessary load on the engine.


Lawrance

[4X4V8]

PO171 and PO174 according to Rave is actually running too rich, not lean as I posted before. Don't trust a random googled fault code website, obviously.

I've just replaced plugs and leads so hopefully that's fixed it. the lead-to-plug connection for cyls 1 and 2 were badly corroded.

TempestV8, I do have a ScanGauge and I am running 91-93 degrees cruising and temp creeps up from 96 to 100-102max fairly quickly when in traffic or parking. I tried holding revs at around 1800rpm at the lights and temp dropped fairly quickly from abt 98 to 96 before the lights changed. As I moved off, of course temp drops to 95 or 94 almost straight away and settles to 91 or so as I keep cruising.

Anyway, I am getting a LR mechanic to look at it next week - he claims the radiator needs to come out at those temps as it suggests a blockage. I'm too paranoid about slipped liner risk to leave it any longer.

Interesting what you say abt the MAF sensor and 02 sensors. If this doesn't fix it, I may have to look at those items...

[duncanw]

Have you seen this thread ?

http://www.aulro.com/afvb/technical-chatter/45317-disco-problems-maybe-maf.html

[Pedro_The_Swift]

What's the best deal on Magnecors in Aus? I can get them from the US for abr $120 plus shipping abt $40 but if it's not much more may as well go local.

Pedro, you're talking Bosch Platinum? No-one likes the OE Champions?

Bosch?:eek:

naw,, sorry,, NGK!;)
(they are the same as a late model holden???)

[tempestv8]

So now that the plugs must be in and the new leads as well, is the economy better?

:)

[4X4V8]

So now that the plugs must be in and the new leads as well, is the economy better?After plugs and leads, the misfiring stopped.

The fault codes still occurred (P0171 and P0174).

I bought a Intermotor afm sensor and since then the P0171 and P0174 fault codes have stopped coming up (so far).

The idling temp seems to stop at 98 for a while but still eventually reaches 102 degrees (which is what it was doing before any of this. I guess this is normal, and although I read a post here where a faulty afm was causing temp increases, there seems to be no correlation in my case.

Afer fitting the new afm, I took the car on a 38km loop from Ashfield to the M5 in Padstow and back in free-flowing traffic and on the ScanGauge consumption dropped pretty quickly to around 14.5L/100km. This is not bad and I think on a highway run it'd drop into the 13s, which is about as good as you'd expect in a D2 V8 (although I fluked 12.8L/100km Canberra-Sydney in my previous D2 V8 auto once, but it must've been with a tailwind).

I have had a few people tell me that non-Bosch afms are rubbish, but for now I am going to wait and see what this one does. Certainly cruising economy is on the money and fault codes are not coming up when they would before. I think there might be a slight hesitation at low revs that was not there before, but can't say with certainty.

Trip meter and refill calculations tend to correlate with the Scangauge results.

However I did get a 14L/100km figure cruising on the M4 before any of this, and I can't tell if performance is any better, so I really don't know if what I did was just preventative maintenance. The problem is that I don't have time to drive the D2 much and when I do find an excuse to drive it, it is usually to run errands over short distances - and maybe that's why it was averaging 25L/100km. I need to give it a good shakedown run.

Anyway, my new leather ES steering wheel has arrived from the US and a it made me feel so much better about my D2's economy ;)

[simonl8353]

Ahhhhh the new leather steering wheel eases the burden somewhat.

Dont be too hard on the fuel consumption your getting. I get 15L/100k on a run/camp/4WD/run home trip and last week 23.5L/100k for a mixture of short runs, medium runs, school pick ups (less than 1k, I wonder where my wife left her legs!) and w/end trips to local Bunnings etc. All driven all without flooring the big fat GO pedal.

Worst ever was 30L/100k.

Hey, when we V8 drivers have finished with the worlds oil reserves, does that mean War everywhere will stop. Think about it;)

[Pedro_The_Swift]

also means all those noisey smelly rattlers will stop:p

[simonl8353]

SNAKES !
what have they got to do with it?

[Measurer]

4X4,
the occasional miss is the interesting thing. I have just replaced the coils for both V8 banks along with new leads & platinum plugs. Car averages between 14 & 15 litres/100kms & is a pleasure to drive. Alos, it has a Bruce Davis ECU chip mod. Car has plenty of torque & the cost of the chip was worth it. The cost of the coil replacement was aound $0.9k as a result of the plennum having to removed to get to them.

[tempestv8]

My ECU has started logging P0171 recently and more recently P1171 and P1174 codes as well.

I got the adaptations reset, and the engine stalled. When I started up the engine again, it idled roughly, like it wasn't running properly, which was quite surprising because this meant that the ECU had been compensating for some issue.

I've been told that if Bank 1 (passenger side in Australia) runs lean, it's often the case that the MAF has failed.

MAF was replaced with a known good one and the engine was good. Refitted my MAF and engine started running rough again. So it was a new MAF for me that fixed my problem. (How ironic that I posted this very thing on this thread not too long ago!)

:angel:

[Grumndriva]

I think all Disco MAFs are rubbish. I have replaced the original in mine three times in 90,000 km, and I am getting sick of doing so. They are just not of merchantable quality. My experience was that the fuel flow increased substantially, in part because you need so much more accelerator to get normal performance. In my case I notice that with a dead MAF the vehicle stays in third until around 80, whereas with a working one it normally changes into top at around 60.

Some of the fuel flows mentioned seem very high to me. Even with the 4.6 I still get around 13 LHK on a trip at 100-110, and around 17-18 in town. Towing a 2.5 tonne dirt road van I get around 26 LHK, but it varies a lot with wind direction and speed due to the van's dreadful aerodynamics.

4X4 V8, I never thought I would see someone put "economy" in the same sentence as "Disco V8". Good to see it is running better now.

[grumpybastard]

D2 MAF sensor-cross reference

Just replaced my MAF earlier in the week *sigh* and just read this thread this morning :(